I don't mean to be picking on you but, running "top tier fuel" has no affect on the backs of the intake valves how do you figure? Fuel isn't coming from the intake manifold it's directly injected into cylinder at the top of combustion chamber, although top tier fuel might help keep the injectors cleaner longer.
Where did you see this cleaning service for $150-200. I know BG has all sorts of cleaners and special tools to do this type of service but I don't think it's the price you stated is it?
If you haven't watched it you should...
https://www.youtube.com/watch?v=RnhUJsZXzmg Not sure if Oil Catch Can will work either I've seen mixed reviews some say it works other say it doesn't catch anything, If I were to use one though I'd find one that doesn't eliminate the stock PVC many of them do.
Basically the only way to solve this problem is manual cleaning which requires removal of the intake manifold. It would be nice if someone came up with a intake manifold kit (like little injectors) that could be put into the air stream for each runner that you could periodically add cleaners to, you wouldn't
have to worry about running harsh chemicals thru the turbo and other parts could damage engine. I've heard the BG products are very good but haven't found any service shops around here, every 10kmi I'd go that route if I could find a dealer to do it (if it wasn't too expensive)
Manufactures have gone with direct injection to get better gas mileage but what savings are we actually seeing if you have to spend $500-1000 to have valves cleaned every 40-50kmi not to mention the injectors themselves.